1. Field of the Invention
The present invention relates to an aerodynamic lens, and more particularly to an aerodynamic lens capable of effectively focusing nanoparticles in a wide range, whose focusable size range is approximately two order of magnitude, e.g., 30˜3,000 nm.
2. Description of the Related Art
As well known in the art, an aerodynamic lens focuses particles floating in the atmosphere to generate a particle beam. The aerodynamic lens is generally used together with a single particle mass spectrometer (SPMS) that analyzes chemical composition and size of a single particle in an aerosol state.
Such an aerodynamic lens is configured with multi-stage orifices and focuses particles by means of shrinkage/expansion of a carrier gas and inertia of the particles without any special mechanical or electric device. However, aerodynamic lenses suggested until now may focus particles whose particle sizes are just in the range of about 3˜30 nm or 30˜300 nm, where a maximum size is just about 10 times of a minimum size.
The range of focusable particle sizes is limited as above because too small particles are not easily focused and too great particles cause collision losses due to the inertia. Considering that the range of particle sizes allowing highly efficient focusing is limited as above, it is also impossible to efficiently focus particles with more variable sizes.
In addition, in case of an orifice nozzle provided at an outlet of a conventional aerodynamic lens, air is abruptly expanded at an outlet of the nozzle due to a great pressure difference between the front and rear portions of the nozzle throat, and after that, the velocity of the air is greatly decreased due to the compressibility effect. Such an air expansion/compressibility effect causes the air velocity to be relatively increased in a radial direction of the lens, thereby disturbing the focusing of a particle beam.